ImageDerivative:

-------------------------------------------------------------------------------
   Generate an image derivative. 
   The default it the mask a = [1 2 1;0 0 0;-1 -2 -1]/8 (Sobel)
   but any mask can be input.
-------------------------------------------------------------------------------
   Form:
       ImageDerivative;
       ImageDerivative( i );
   d = ImageDerivative( i, n )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   i              (n,m)     Grayscale image (double)
   a              (:,:)     Kernel

   -------
   Outputs
   -------
   d              (n,m)     Derivative

-------------------------------------------------------------------------------

Children:

Imaging: ImageProcessing/ColorMapGrayScale
Imaging: ImageProcessing/Imager
Imaging: Utilities/ReadImage